1.8 Meridional and Vertical Mass Flux

Figure 2.18 shows the latitude-altitude cross section of mean mass flux for the four seasons. Mass flux is the rate of transfer of mass through an area per unit time and is positive when the flux is upward or poleward. A pattern of alternating positive and negative mass flux is seen in the figure and defines some major features:

a. There are three-cell patterns evident in each hemisphere.

b. The cells with rising motion in near-equatorial latitudes and sinking motion in the subtropics are known as the Hadley circulation or Hadley Cell (Huschke, 1957). The circulation is strongest during the winter seasons with the upward motion extending across the equator into the opposite hemisphere.

c. The cells with rising motion around 60° latitude and sinking motion in the subtropics are known as the Ferrel circulation or Ferrel Cell (Fairbridge, 1967). The circulation is strongest during the winter seasons.

d. The Hadley and Ferrel circulations carry heat, moisture and momentum with them, and are responsible for the poleward transport of total energy.

Section 1.7 Section 1.9

Chapter 2